Fluid operated brake arrangements for large material hauling vehicles, such as trucks and the like, are being continually improved in an attempt to achieve safe and effective braking under severe operating conditions. Representative of these braking arrangements are the following U.S. Pat. Nos.: U.S. Pat. No. 2,928,504, issued Mar. 15, 1960 to E. H. Hahn et al U.S. Pat. No. 3,547,233, issued Dec. 15, 1970 to J. H. Girvan, U.S. Pat. No. 3,547,234, issued Dec. 15, 1970 to C. F. Cummins et al, U.S. Pat. No. 3,613,839, issued Oct. 19, 1971 to S. I. MacDuff, U.S. Pat. No. 3,770,085, issued Nov. 6, 1973 to E. R. Cottingham.
While these brake arrangements have advanced the state of the art, they have not effectively integrated service braking with emergency and/or parking braking in a single annularly compact and economical package. For example, it is substantially imperative that such brake arrangements be small in size, while having a relatively high multi-purpose capacity in order for them to fit within a wheel rim and encirclingly around an axle housing where space is at a premium. Another desirable characteristic is the ability to easily install or remove them as a modular package.
In the past, in order to increase the capacity of an individual brake arrangement, there has been a tendency to incorporate a larger number of separate brake engagement mechanisms about the periphery of the member to be braked. This not only requires a larger number of the same parts at added expense, but also presents the potential problem of unequal peripheral loading of the braked member, should service problems develop in one or more of the individual mechanisms. Furthermore, many of these mechanisms are complex and costly to manufacture.
Another major deficiency with respect to most prior art brake arrangements is that they do not make any provision for supplying a cooling fluid to the energy absorbing surfaces. As a result, both the service life and the capacity of the brake arrangement is adversely affected.